Are a vulnerability & a weakness the same thing?

This question got me thinking about my vulnerabilities:

http://www.fluther.com/disc/82977/how-much-do-you-show-your-vulnerabilities/

I do not show them often and I know that’s a problem. I admire people who do show them. So, I was just sitting down to write out a list of my own vulnerabilities and it made me wonder, what EXACTLY is a vulnerability? is it the same thing as a weakness? I can write out a list of my weaknesses (both character & job skill weaknesses) but to me that doesn’t seem the same as a vulnerability. Isn’t a vulnerability a thing that makes you more susceptible to attack by others?

So, how would you describe a vulnerability from your own experience (not a dictionary)?